Ortiz-de-Zárate, Victoria

Pérez-Guerrero, Bernardo

English

Annual geographical distribution of Spanish troll fleet activity is estimated by means of
sampling scheme based on a number of interviews to skippers carried out at landings in main
fishing ports of the Spanish Atlantic and Bay of Biscay coast. The compiled geographical
position by trip on latitude and longitude (1x1 degrees) is mapped on monthly bases for each
year. Troll fleet targets albacore (Thunnus alalunga) from June to November operating in
offshore waters of the northeast Atlantic and Bay of Biscay. Based on the compiled information
of the interviews, i the spatial evolution of the troll fleet fishing ground for the fishing seasons
from 2000 to 2013 t is presented

Ortiz-de-Zárate, V. (Victoria)

Pérez-Guerrero, B. (Bernardo)

Repositorio Institucional Digital del IEO

SCRS/2015/025 Collect. Vol. Sci. Pap. ICCAT, 72(8): 2016-2022 (2016) 2016 EVOLUTION OF SPATIAL DISTRIBUTION OF FISHING  GROUND FOR THE SPANISH ALBACORE (THUNNUS ALALUNGA)  TROLL FLEET IN THE NORTH EASTERN ATLANTIC, YEARS: 2000 TO 2013  V. Ortiz de Zárate1, B. Perez1     SUMMARY  Annual geographical distribution of Spanish  troll fleet activity is estimated by means of sampling scheme based on a number of  interviews to skippers  carried out at landings in main fishing ports of the Spanish Atlantic and Bay of Biscay coast. The compiled geographical position by trip on latitude and longitude (1x1 degrees) is mapped on monthly bases for each year. Troll fleet targets albacore (Thunnus alalunga) from June to November operating in offshore waters of the northeast Atlantic and Bay of Biscay. Based on the compiled information of the interviews, i the spatial evolution of the troll fleet fishing ground for the fishing seasons from 2000 to 2013 t is presented.    RÉSUMÉ  La répartition géographique annuelle de l'activité des flottilles de ligneurs espagnols est estimée au moyen d'un plan d'échantillonnage basé sur un certain nombre d'entretiens réalisés auprès des capitaines au débarquement dans les principaux ports de pêche de la côte atlantique espagnole et du golfe de Gascogne. La position géographique compilée par sortie par latitude et longitude (1º x 1º) est illustrée sur une carte sur une base mensuelle pour chaque année. Les flottilles de ligneurs ciblent le germon (Thunnus alalunga) de juin à novembre, opérant dans les eaux au large du Nord-Est de l'Atlantique et du golfe de Gascogne. D'après les renseignements obtenus des entretiens, l'évolution spatiale de la zone de pêche de la flottille de ligneurs pour les saisons de pêche de 2000 à 2013 est présentée.  RESUMEN  La distribución geográfica anual de la actividad de la flota de cacea española se estima por medio del esquema de muestreo basado en un número de encuestas realizadas a los patrones en el momento de la descarga de las capturas en los principales puertos de la costa atlántica española y del golfo de Vizcaya. La información geográfica en latitud y longitud (1ºx1º) por marea se representa en mapas mensuales para cada año. La flota de cacea se dirige al atún blanco (Thunnus alalunga) desde junio a noviembre en las aguas oceánicas del Atlántico nordeste y del golfo de Vizcaya. Con la información recogida en las encuestas, se presenta la evolución espacial del área de pesca de la actividad pesquera de la flota de cacea desde 2000 hasta 2013.  KEYWORDS  Thunnus alalunga, Troll fishery,  Fishing ground, Spatial evolution, Northeast Atlantic, Albacore                                                           1 Instituto Español de Oceanografía. Apdo.240. 39080 Santander. Spain.  HUvictoria.zarate@st.ieo.es U  2017 1. Introduction  Albacore (Thunnus alalunga) has been targeted by the Spanish surface fleet, with baitboat and  troll  vessels for decades in the North eastern Atlantic and Bay of Biscay offshore waters  (Arrizabalaga et al., 2010, Ortiz de Zárate and Barreiro, 2010). The albacore fishery represents an important resource from the socio-economical activity reported in the north-western and northern fishing ports. In spring and early summer, as the water temperature rises, immature albacore  migrates from the central Atlantic waters towards the north-eastern Atlantic and Bay of Biscay temperate surface waters, (Aloncle et Delaporte, 1973; Bard, 1981;  Ortiz de Zárate and Cort, 1998; Arrizabalaga, 2003) where forage prey are abundant (Pusineri et al., 2005). The oldest fleet targeting albacore in the Bay of Biscay area and Atlantic waters is the troll fleet (Bard and Santiago, 1999). In his historical compilation, they recovered Spanish troll catches since 1930.    Concerning the activity of both fleets: alive bait boat (BB) and trolling (TR), no major changes were observed during last decades (ICCAT, 2014). The number of boats involved varies among years; the annual averaged number is 450 vessels (80% troll and 20% bait boat). The troll vessels are of lesser tonnage (mean of 50 GRT) than those of bait boat (mean 120 GRT). The catch composition by age is mainly made up of immature albacore 1 to 4 age groups, corresponding to 50 to 90 cm fork length fish.   The troll fleet operated mainly in the offshore waters of the North eastern Atlantic from June to October. Only partially in September and during October the activity of this fleet took place in the Bay of Biscay area. The geographical distribution of bait boat catches in the last two years has been reduced and concentrated mainly in the Bay of Biscay area closer to the coast line. In 2012 and 2013 years, the monthly  spatial distribution of troll vessels interviewed shown a presence of the albacore resource, in offshore Atlantic waters at early fishing season beginning in June until the end of summer season in September, when some few  troll trips showed a distribution in the Bay of Biscay that continued in October. Similar troll fleet behaviour was observed in 2011 fishing season (Ortiz de Zárate et al., 2013)  Fonteneau (2008) hypothesized about a possible shrinking fishing zones of both albacore longline and surface fisheries, and/or to decline in targeting albacore for the longline fleets.   The aim of this paper is to present an overall description of the geographical distribution of catches obtained by the Spanish troll fleet from 2000 to 2013 fishing seasons. Geographical information was collected from the monitoring of the fishery, by means of interviews to skippers that reported an approximate location of 1º by 1º degree within the seasonal albacore fishing grounds in the North Eastern Atlantic and Bay of Biscay area.     2. Material and Methods  The monitoring of the Spanish troll fleets activity was done by means of collecting information through interviews to skippers at main fishing ports located along North western coast and the Cantabrian coast. The information, based on individual trip samples by fleet, that was  collected included: number of days at sea, number of fishing days, catch in number of fish and weight (kg) and an approximate location of catch by 1º x1º degrees latitude and longitude, recording at least one position per trip.   The catch and nominal fishing effort expressed in fishing days information was processed for troll fleet  on monthly basis following raising  procedures to estimate the Task I (catch and effort) statistics of ICCAT (ICCAT, 2006-2010). Thus, the catches presented in this document had been communicated to ICCAT and are included in ICCAT data base. However, nominal catch information (Task I) is assimilated to 5º x 5º degrees squares, due to the lack of  logbooks available, for this fishery.     The geographical position of collected information of catches in weight and fishing effort by trip was aggregated by 1º x 1º latitude and longitude for each month. Fishing season covered from June to October all years and some years extended the fishing activity until November. Likewise, the annual troll (kg) catch   was calculated in percent respecting the total catch of surface fishery vessels in the area: baitboats and trollers. Additionally monthly percentage of catch in weight was calculated for each year analysed from 2000 to 2013, to describe the temporal evolution of catches within each year. Likewise, the number of 1º x 1º squares by month were added and the equivalent area transformed in km2 (1x1 sq = 12,321 km2) for time period examined.    2018 3. Results and Discussion   According to the information collected and processed, the  total albacore nominal catch (Task I data) obtained by the troll  fleet represented a variation on percentage of both fleets,  between  45-50% in most of the years, being the lowest catch in 2000 and at the contrary the highest troll catch was registered in 2013. Looking at the nominal catch, the highest levels registered were obtained in 2005 and 2006 years, representing a record on the years described (Table1). Concerning the percentage of annual troll catch, it is observed in same Table 1, that most of the catch is taken from July to September, approximately from  75 %  to 85 % and the remaining percentage of catch are scattered between both months: June and October. There is an extension of the fishing season to November in some years, but the catch represented less than 1%.   Due to the catch been mostly taken in the summer months July to September in the period described, only these months were chosen to represent the geographical distribution accordingly to the information gathered from  interviewed skippers, only one position per trip is shown. Results are shown in Table 2. There is not a clear trend from 2000 to 2013, although both 2006 and 2008 years, shown the highest and the lowest number of 1º by 1º degrees squares reported. Last 2013 year would represent and average between the lowest and the highest number of squares covered.   The temporal evolution by month of the geographical representation in 1º by 1º degrees for June, July and August for the time period described, 2000 to 2013 years, is shown in Figure 1.a. It can be stressed that the overall area concerning latitudinal displacement has been quite stable, reaching 50 º North and over along the time series.   However, the Bay of Biscay shown a decrease of presence of trollers beginning in 2009. This separation between both fishing grounds: oceanic and Bay of Biscay, is more apparent when looking at Figure 1.b, that represents the September trip locations beginning in 2009 until 2013. Moreover, there is a discontinuity appearing between the area of Bay of Biscay and the oceanic waters of North Eastern Atlantic fishing grounds, also initiating in 2010. Fewer number of locations are displayed those years. This is in agreement with the lowest percentage of catches taken in the Bay of Biscay area during the highest season months represented by July and August in Table 3. As shown,  less than  the 10% of catch for the highest season months (July and August) was taken in the Bay of Biscay from 2009 to 2013, but 2012, were catches represented 31% and 23% of the total taken in July and August respectively in that year   The inter annual changes observed in the troll fishery concerning the spatial distribution that had been observed since 2009 until 2013, in this document merit to be studied in relation to factors such the availability of prey to forage, the habitat utilization by immature albacore (Pusineri et al., 2005; Goñi et al., 2009) along with knowledge of climatic and oceanographic conditions in the northeast Atlantic waters and Bay of Biscay off shore waters. All these related variables impacting the migratory behaviour of albacore (Dufour et al., 2010). Albacore migratory behaviour component in relation with the physical environment requires comprehensive studies.   Acknowledgements  The authors would like to thank all the network sampling staff involved in the collection of fisheries data at main fishing ports in Galicia and Cantabrian coast. The work related to this document was partly supported by the IEO project PNDB 2011-2013 funded by DG MARE of European Union.      2019 References   Aloncle, H. et F. Delaporte. 1973. Populations, croissance et migrations du germon (Thunnus alalunga) dans le  nord-est Atlantique essai de synthèse. Rev. Trav. Inst. Pêches marit., 37(1): 97-115.   Arrizabalaga, H., J. Santiago, Y. Sagarminaga, I. Artetxe. 2010. Daily CPUE database for Basque albacore  trollers and baitboats Collect. Vol. Sci. Pap. ICCAT, 65(4): 1291-1297  Bard, F.X. 1981. Le thon germon (Thunnus alalunga) de l’Ocean Atlantique. De la dynamique de population à  la stratégie démographique. Thèse Doctorat ès Sciences Naturelles, Universitè de Paris VI, 330 p.  Bard, F.X and J. Santiago.1999. Review of albacore (Thunnus alalunga) historical surface fisheries data (1920- 1975) for possible relationships with north Atlantic oscillation. SCRS/98/106. ICCAT, Col. Doc. Cient. Vol.  49 (4): 311-323.  Dufour, F., H. Arrizabalaga, X. Irigoien, J. Santiago. 2010. Climate impacts on albacore and bluefin tunas  migrations phenology and spatial distribution. Progress in Oceanography, 86, 283-290.  Fonteneau, A. 2008. Some comments upon the 2007 North Atlantic Albacore assessment SCRS/2007/155,  Collect Vol. Sci. Pap. ICCAT, 62, 944–950, 2008  Goñi, N. I. Arregui, A. Lezama, H. Arrizabalaga and G. Moreno. 2009. Small scale vertical behaviour of  juvenile albacore in relation to their biotic environment in the Bay of Biscay.    J.L.Nielsen et al. (eds.). Tagging and tracking of Marine Animals with Electronic Devices. Reviews: Methods  and Technologies in Fish Biology and Fisheries 9, DOI 10.1007/978-1-4020-9640-2-4. © Springer  Science+Business Media B.V.   ICCAT. 2006- 2009. ICCAT Manual. International Commission for the Conservation of Atlantic Tuna. In:  ICCAT Publications [on-line]. Updated 2009. [Cited 01/27/]. ISBN (Electronic Edition): 978-92-990055-0-7  Ortiz de Zárate, V. and J. L. Cort. 1998. Albacore (Thunnus alalunga, Bonnaterre) stock structure in the Atlantic  Ocean, as inferred from distribution and migration patterns. ICCAT, Col. Vol. Sci. Pap. 50 (1): 251-260.  Ortiz de Zárate, V. and  S. Barreiro. 2010. Statistics from the Spanish albacore (Thunnus alalunga) surface  fishery in the North eastern Atlantic in 2008. Collect. Vol. Sci. Pap. ICCAT, 65(4): 1437-1445.  Pusineri, C., Y. Vasseur, S. Hassani, L. Meynier, J. Spitz, and V. Ridoux. 2005. Food and feeding ecology of  juvenile albacore, Thunnus alalunga, off the Bay of Biscay: a case study. ICES Journal of Marine Science,  62: 116e122. doi:10.1016/j.icesjms.2004.09.004  2020 Tabla 1. Nominal match of Troll fleet, percent of surface fishery, fishing effort and monthly percentage.   TR+BB Troll (TR) Effort (TR) Monthly TR Catch  % Years Catch (%) Catch (Kg) Fish Days 6 7 8 9 10 11 2000 32.3 5,012,643 12,023 13.4 40.0 38.2 7.6 0.7 0.0 2001 55.4 4,244,596 8,512 16.0 26.3 36.3 20.3 1.1 0.0 2002 52.5 3,976,390 11,067 8.3 33.1 33.5 18.9 6.1 0.1 2003 46.4 5,192,711 11,142 5.0 36.1 37.5 14.2 7.2 0.0 2004 51.1 7,476,716 10,101 6.0 48.4 27.4 11.4 6.5 0.4 2005 52.2 10,164,611 11,733 9.3 34.7 30.5 18.4 7.1 0.0 2006 42.6 10,276,785 12,484 6.7 35.3 36.3 15.6 6.0 0.0 2007 42.9 6,088,754 10,652 6.8 31.0 31.6 16.5 14.0 0.1 2008 44.0 5,233,415 6,628 5.3 52.1 19.7 19.0 3.7 0.2 2009 47.6 4,437,192 5,875 13.3 47.5 23.1 6.5 8.9 0.7 2010 56.3 7,009,462 8,548 6.4 48.0 31.4 7.3 6.5 0.5 2011 45.1 3,564,082 6,910 8.3 47.9 20.4 16.6 6.4 0.4 2012 48.5 5,832,738 7,630 10.2 27.7 29.1 21.7 10.6 0.7 2013 63.1 5,863,839 6,935 4.3 50.2 32.2 10.5 2.6 0.1   Tabla 2. Information collected from monthly number of 1ºN x 1ºW squares and area covered.       N 1ºx1º sq Area (Km2) (1ºx1º sq=12,321 km2) Years Jul Aug Sep Total Jul Aug Sep Total 2000 62 66 28 156 763,902 813,186 344,988 1,922,076 2001 52 40 33 125 640,692 492,840 406,593 1,540,125 2002 73 34 26 133 899,433 418,914 320,346 1,638,693 2003 47 56 16 119 579,087 689,976 197,136 1,466,199 2004 69 49 39 157 850,149 603,729 480,519 1,934,397 2005 61 54 50 165 751,581 665,334 616,050 2,032,965 2006 60 60 50 170 739,260 739,260 616,050 2,094,570 2007 44 53 37 134 542,124 653,013 455,877 1,651,014 2008 41 35 24 100 505,161 431,235 295,704 1,232,100 2009 47 48 12 107 579,087 591,408 147,852 1,318,347 2010 26 47 36 109 320,346 579,087 443,556 1,342,989 2011 51 54 35 140 628,371 665,334 431,235 1,724,940 2012 53 38 26 117 653,013 468,198 320,346 1,441,557 2013 58 44 37 139 714,618 542,124 455,877 1,712,619 Total 744 678 449 1871 9,166,824 8,353,638 5,532,129 23,052,591           2021 Tabla 3. Catch reported in Bay of Biscay area (43º- 47ºN / 0º- 10ºW, BofB) for Troll fleet.    July August  BofB (kg) Total (kg) % BofB BofB (kg) Total (kg) % BofB 2010 61,283 2,631,827 2 93,384 1,849,512 5 2011 13,711 1,602,605 1 32,865 570,672 6 2012 233,967 745,985 31 314,205 1,367,979 23 2013 31,844 381,317 8 33,559 292,166 11     30 25 20 15 10 5 0 5 10303540455055ALB TR 2000JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2001JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2002JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2003JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2004JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2005JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2006JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2007JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2008JulAug2022       Figure 1.a. Distribution of the Spanish fleet trolling from 2000-2013 fishing season (July-August) derived from interviews to skippers.                                                     Figure 1.b. Distribution of the Spanish troll fleet in the fishing season (September) derived from interviews to skippers. Years: 2009-2013.          30 25 20 15 10 5 0 5 10303540455055ALB TR 2009JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2010JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2011JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2012JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2013JulAug30 25 20 15 10 5 0 5 10303540455055ALB TR 2009Sep30 25 20 15 10 5 0 5 10303540455055ALB TR 2010Sep30 25 20 15 10 5 0 5 10303540455055ALB TR 2011Sep30 25 20 15 10 5 0 5 10303540455055ALB TR 2012Sep30 25 20 15 10 5 0 5 10303540455055ALB TR 2013Sep

Evolution of spatial distribution of fishing ground for the Spanish albacore (Thunnus alalunga) troll fleet in the North Eastern Atlantic, yeras: 2000 to 2013.

Annual geographical distribution of Spanish troll fleet activity is estimated by means of
sampling scheme based on a number of interviews to skippers carried out at landings in main
fishing ports of the Spanish Atlantic and Bay of Biscay coast. The compiled geographical
position by trip on latitude and longitude (1x1 degrees) is mapped on monthly bases for each
year. Troll fleet targets albacore (Thunnus alalunga) from June to November operating in
offshore waters of the northeast Atlantic and Bay of Biscay. Based on the compiled information
of the interviews, i the spatial evolution of the troll fleet fishing ground for the fishing seasons
from 2000 to 2013 t is presented.S

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http://www.repositorio.ieo.es/e-ieo/bitstream/10508/10360/1/CV072082016.pdf

Evolution of spatial distribution of fishing ground for the Spanish albacore (Thunnus alalunga) troll fleet in the North Eastern Atlantic, yeras: 2000 to 2013.

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